Natural prostaglandins (hereinafter sometimes referred to as PG) are compounds which have singular biological activities including platelet aggregation inhibiting activity, blood pressure lowering activity, etc., and are useful natural substances which have recently been used as remedies for peripheral circulatory disorders in the medical field. Among prostaglandins, prostaglandins A are known as ones which have a double bond in their cyclopentenone ring and, for instance, prostaglandin A.sub.2 is expected as the drug to display blood pressure lowering activity (E. J. Corey et al., J. Amer. Chem., 95, 6831 (1973)).
It has been reported that prostaglandin A series have a realizable possibility of becoming antitumor agents in view of their strong action to inhibit the synthesis of DNA (Biochem. Biophys. Res. Commun. 87, 795 (1979); W. A. Turner et al., Prostaglandins Relat. Lipids, 2, 265-8 (1982)).
M. Fukushima et al. examined the effect of PGD.sub.2 to inhibit proliferation of L1210 mouse leukemia cells and human leukemia cell lines, and reported the IC.sub.50 of PGD.sub.2 on L1210 cells is 2.4 micrograms/ml (Biochem. Biophys. Res. Commun., 105, 956 (1982)).
On the other hand, U.S. Pat. No. 3,755,426 disclosed the 10-halogenated-derivatives of prostaglandins A which have broncho-dilator activity and blood pressure lowering activity, but this patent contains no disclosure concerning the possibility of their use as antitumor agents.